Beam profile is one of the key performance indicators for high-intensity proton accelerators. A new residual gas ionization profile monitor has been installed at the Linac of the China Spallation Neutron Source for non-destructive, real-time measurement of parameters such as the transverse beam profile at critical locations. This paper presents the selection, structural design rationale, and beam test results of this profile monitor. The detector adopts a compact structure, offering a high-resolution design within a limited space. The compact design eliminates the equipotential strips that uniformly act on the electric field and adds a field grid at the lower plate apertures to improve the uniformity of the electric field and reduce the electric field components. Beam tests evaluated the performance of the new detector in measuring orbit and profile parameters, with calibration performed in comparison to the BPM near the detector’s location. The error between the transverse profile measurement and theoretical calculation was less than 8.3%, meeting the beam measurement requirements.